Singlet oxygen lifetime changes in dying glioblastoma cells

Abstract

Time‐resolved phosphorescence detection was employed to determine the lifetime of singlet oxygen in live cells. Using hypericin as a photosensitizer, singlet oxygen was generated in U87MG glioblastoma cells. The phosphorescence of singlet oxygen was detected in aqueous cell suspensions following pulsed laser excitation. Our goal was to eliminate or reduce the problems associated with lifetime measurements in water‐based cell suspensions. The apparatus enabled simultaneous singlet oxygen phosphorescence and transient absorption measurements, reducing uncertainty in lifetime estimation. The changes in singlet oxygen lifetime were observed during early and late apoptosis induced by photodynamic action. Our findings show that the effective lifetime of singlet oxygen in the intracellular space of the studied glioblastoma cells is 0.4 μs and increases to 1.5 μs as apoptosis progresses. Another group of hypericin, presumably located in the membrane blebs and the plasma membrane of apoptotic cells, generates singlet oxygen with a lifetime of 1.9 μs.

Design of AsLOV2 domain as a carrier of light‐induced dissociable FMN photosensitizer

“…The experimental apparatus used for 1 O 2 detection was described in detail elsewhere (Hovan et al, 2023). Briefly, short 5‐ to 7‐ns‐long laser pulses with 475‐nm wavelength originating from an optical parametric oscillator pumped by an Nd: YAG Q‐switched laser excited 25 μM AsLOV2 samples (2 mL) at 10 Hz frequency.…”

“…The time‐resolved 1 O 2 phosphorescence signal (at 1270 nm) was measured on a photomultiplier tube (Hamamatsu H10330A‐75), in photon counting mode, connected to a multichannel scaler PCI card (Becker&Hickl, MSA‐300). Spectral background was subtracted from the signal as explained in our previous study (Hovan et al, 2023). Two additional band‐pass filters were used to detect the background in the spectral regions neighboring the 1270 nm 1 O 2 peak.…”